Allow prefix :: in constructed dhcp-range.

man/dnsmasq.8

@@ -663,6 +663,14 @@ equal either the start or end address given in the dhcp-range. This is
 to prevent prefixes becoming perpetual if the interface 
 gains a SLAAC address for the prefix when it is advertised by dnsmasq.
 
+If a dhcp-range is only being used for stateless DHCP and/or SLAAC,
+then the address can be simply ::
+
+.B --dhcp-range=::,constructor:eth0
+
+This removes the condition above, and will pick up the prefix from any address on eth0 which is NOT 
+autoconfigured, slaac, temporary or deprecated.
+
 There is a variant of the constructor: syntax using the keyword
 .B constructor-noauth.
 See 

src/dhcp6.c

@@ -539,7 +539,9 @@ static int construct_worker(struct in6_addr *local, int prefix,
 	
       }
     else if ((addr6part(local) == addr6part(&template->start6) ||
-	      addr6part(local) == addr6part(&template->end6)) && 
+	      addr6part(local) == addr6part(&template->end6) ||
+	      (IN6_IS_ADDR_UNSPECIFIED(&template->start6) &&
+	       IFACE_PERMANENT == (flags & (IFACE_PERMANENT | IFACE_DEPRECATED)))) && 
 	     wildcard_match(template->template_interface, ifrn_name))
       {
 	start6 = *local;